What are valid characters for Windows environment variable names and values?

Question

After some reseach, I found out that length limits for names are 255 and for values 32767 characters.

But which characters are allowed for names?
And wh

Answer 1

It seems like <>^&| are also valid characters, as long as they are properly escaped:

C:\>set ^<^>^^^&^|=xyz

C:\>echo %<>^&|%
xyz